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| /**
* @param bimg0 low exposure image
* @param shutter time for low exposure image
* @param bimg1 mean exposure image
* @param shutter time for mean exposure image
* @param bimg2 high exposure image
* @param shutter time for high exposure image
* @return merged image
*/
public static BufferedImage merge(BufferedImage bimg0, float t0, BufferedImage bimg1, float t1, BufferedImage bimg2, float t2) {
// output image
int width = bimg0.getWidth(), height= bimg0.getHeight();
BufferedImage out = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// work image (HSB colorspace)
float[][][] image = new float[width][height][3];
// structure returned by Color.RGBtoHSB
float[] hsb0 = new float[3];
float[] hsb1 = new float[3];
float[] hsb2 = new float[3];
// min/max in work image
float min=Float.MAX_VALUE, max=0;
// create work image
for(int y=0;y<height;y++) {
for(int x=0;x<width;x++) {
// HSB pixel in image low
int r0 = bimg0.getRaster().getSample(x, y, 0);
int g0 = bimg0.getRaster().getSample(x, y, 1);
int b0 = bimg0.getRaster().getSample(x, y, 2);
Color.RGBtoHSB(r0, g0, b0, hsb0);
// HSB pixel in image mean
int r1 = bimg1.getRaster().getSample(x, y, 0);
int g1 = bimg1.getRaster().getSample(x, y, 1);
int b1 = bimg1.getRaster().getSample(x, y, 2);
Color.RGBtoHSB(r1, g1, b1, hsb1);
// HSB pixel in image high
int r2 = bimg2.getRaster().getSample(x, y, 0);
int g2 = bimg2.getRaster().getSample(x, y, 1);
int b2 = bimg2.getRaster().getSample(x, y, 2);
Color.RGBtoHSB(r2, g2, b2, hsb2);
// brightness dynamic in each image
float slope0 = Math.abs(hsb0[2]-0)/(t0-0);
float slope1 = Math.abs(hsb1[2]-hsb0[2])/(t1-t0);
float slope2 = Math.abs(hsb2[2]-hsb1[2])/(t2-t1);
// best brightness dynamic
float slope = Math.max(Math.max(slope0,slope1), slope2);
// extrapolate brightness using best image
float tf=10*t2;
if (slope==slope0) {
image[x][y][0]=hsb0[0];
image[x][y][1]=hsb0[1];
image[x][y][2]=hsb0[2]+(tf-t0)*slope0;
} else if (slope==slope1) {
image[x][y][0]=hsb1[0];
image[x][y][1]=hsb1[1];
image[x][y][2]=hsb1[2]+(tf-t1)*slope1;
} else if (slope==slope2) {
image[x][y][0]=hsb2[0];
image[x][y][1]=hsb2[1];
image[x][y][2]=hsb2[2]+(tf-t2)*slope2;
}
// save min/max value
if (image[x][y][2]>max) max=image[x][y][2];
if (image[x][y][2]<min) min=image[x][y][2];
}
}
// stretch brightness in range [0,1]
for (int y=0; y<height; y++)
for (int x=0; x<width; x++)
image[x][y][2] = (image[x][y][2]-min)/(max-min);
// 16 bits histogram for brightness
int hsize = (1<<16);
long[] histo = new long[hsize];
for (int y=0; y<height; y++) {
for (int x=0; x<width; x++) {
int v16bits = (int) ((hsize-1)*image[x][y][2]);
histo[v16bits]++;
}
}
// Cumulative distribution function
long[] cumul = new long[hsize];
cumul[0]=histo[0];
for (int i=1; i<hsize; i++)
cumul[i]=cumul[i-1]+histo[i];
// optimal value per bin (equalization)
float bin = (float)(width*height)/(hsize-1);
// equalization lookup table
float[] lookup = new float[hsize];
for (int i=0; i<hsize; i++)
lookup[i] = cumul[i]/bin;
// replacing brightness
for(int y=0;y<height;y++) {
for(int x=0;x<width;x++) {
int v16bits = (int) ((hsize-1)*image[x][y][2]);
float v = lookup[v16bits]/hsize;
image[x][y][2] = v;
}
}
// convert HSB (float) to RGB (24bits)
for(int y=0;y<height;y++) {
for(int x=0;x<width;x++) {
int rgb = Color.HSBtoRGB(image[x][y][0], image[x][y][1], image[x][y][2]);
out.setRGB(x, y, rgb);
}
}
return out;
} |
création d'image HDR
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